Reports say missile strikes on military sites in northern Syria overnight reportedly killed a number of pro-government fighters, including Iranians.
The Syrian military said facilities in Hama and Aleppo provinces were struck.
It did not say if there were any casualties. But a UK-based monitoring group said four Syrians and 22 foreigners, mostly Iranians, died.
It is not known who was behind the attacks. Western nations and Israel have previously hit sites in Syria.
Earlier this month, the US, UK and France bombed three facilities they said were associated with the Syrian government’s alleged chemical weapons programme.
Israel is alleged to have hit an airbase reportedly serving as an Iranian drone command centre and containing an advanced Iranian air defence system. Seven Iranians were among 14 military personnel killed in that attack.
Israel has repeatedly vowed to stop Iran from strengthening its military presence in Syria, where it has deployed hundreds of troops since the country’s civil war began in 2011 to help keep President Bashar al-Assad in power.